It is interesting to note that during the most recent product intros, iMacs have been the computers on stage running the presentations. Clearly, a company such as Apple would want to "show off" their very best.
No. Apple wants to show off what people buy. iMacs outsell Mac Pros by an order of magnitude. The large dog and pony shows are not niche shows. They are productions for a broad audience. They should show what the broad audience may buy for desktop options.
Besides it is neater ( less cabling , set-up ,etc. ) to use iMacs on stage.
If anything the demo would be of the Apple Cinema Display and not the Mac Pro if they decoupled the display from the Mac.
While I agree with a lot of you that Apple given their history, we should not expect too much from them, we can at least hope that the next machine would end up with this 10 core chip.
It is about as equally likely going to get a Sandy Bridge Mac Pro out of Apple sometimes in 2013. Especially if Intel is slow rolling the E5 1600 series closer to Q4.